I. Field of the Invention
The present invention relates to speaker enclosures and, in particular, the present invention relates to an improved speaker enclosure having an upright horn designed to amplify the efficiency of a wide-range driver mounted at the throat of the horn such that the sound emitted from the rear of the driver may be added to the sound emitted from the front of the driver.
II. Description of the Prior Art
In the prior art it has been recognized that in order to construct a speaker enclosure two factors must be considered in conjunction with each other; first, the speaker or driver and, secondly, the baffle or house in which the driver is mounted. In the design and construction of a speaker enclosure, the speaker may first be chosen to determine the type of enclosure to be constructed or the choice of enclosures desired may be used to dictate the required parameters of the speaker. Obviously, when decor, size, and limited available placements in a room are the ruling factor, good design techniques consist of selecting the enclosure and matching the optimum speaker with the selected enclosure. If performance is the main objective, the speaker is first chosen and the disclosure is designed to provide a maximum utilization of the potential inherent in the selected driver.
A speaker by itself causes interference with its own output, and this is primarily due to the fact that the surface which moves the air (called the diaphragm or cone) causes the air to move in both the front and back of the surface. Thus, the diaphragm or cone generates simultaneous impulses which, unfortunately, are out of phase with one another. This means that, if the impulses are allowed to meet, they will cancel each other. Therefore, it has been a primary purpose of the prior art structures to separate the front of the diaphragm or cone from the back of the diaphragm or cone. If this is not accomplished, a large percentage of the energy fed into the speaker will be wasted in the fight between the air moved on either side of the diaphragm or cone surfaces.
Of the four basic forms in which a separation can be obtained, the finite baffle is the most commonly encountered in the furniture-type consoles and generally consists of a board of approximately two-square feet with the speaker mounted in the center. This board forces the back radiation from the diaphragm or cone to travel along a path to reach the other side.
The infinite baffle type of construction is a second approach in use and, in theory, assumes that a speaker mounted on a board of infinite length and width will prevent the back radiation from ever meeting the front radiation, and no cancellation may take place. Thus, the only determining factor would be the ability of the speaker to move enough air at very low frequencies to allow it to be audible. Generally, the infinite baffle is constructed by mounting a speaker on a wall so that the front of the diaphragm or cone is in an entirely different room than the rear.
Another approach which has been devised is the bass-reflex enclosure which functions to add the radiation from the rear of the diaphragm or cone to the radiation emitted from the front of the diaphragm or cone. This is generally accomplished by using the volume of air in the enclosure which acts in conjunction with the mass of air entrapped in a tuned port to create an in-phase, additive relationship. This combination of the rear radiation being added in phase to the radiation off the front of the cone results in almost twice the output from any given excursion of the cone than would be expected if the speaker were mounted in an infinite baffle.
The fourth type of projector is known as a horn projector wherein the bass response is substantially increased if the front of the cone is coupled to a long expanding cone. In most types of horns the effect is to present to the small diaphragm at the throat a very high, but consistent, acoustical impedance while transforming the high-pressure, low particle-velocity wave from the surface of the cone into a low-pressure, high particle-velocity wave with a low impedance, matching that of the air in the room as it reaches the mouth of the horn.
Examples of prior art structures known to the inventor include the inventions disclosed in U.S. Pat. Nos. 1,597,611; 1,692,994; 1,760,892; 2,670,053; 2,847,081; 2,955,669; and 3,554,314. While each of these patents disclose apparatus for overcoming certain disadvantages inherent with the prior art apparatuses in an effort to achieve an excellent dispersion and presentation of sound at seating level by means of an inexpensive enclosure and driver arrangement, none disclose an invention of the type which applicant claims herein.